A visor attachment mechanism in a helmet having the above-described structure has conventionally been known, as disclosed in U.S. Patent Application Publication No. 2010/0064406. In the visor attachment mechanism in a helmet disclosed in U.S. Patent Application Publication No. 2010/0064406 (to be referred to as “the visor attachment mechanism of the patent literature” hereinafter), the removal preventing means includes engaging projecting portions that have a substantially semicylindrical shape fallen down sideways and jut out in the regions of the left and right ends of the visor and the vicinities thereof, and a pair of left and right visor attachment portions provided on the movable plate so as to insert and attach the regions including the left and right ends of the visor and the vicinities thereof to the movable plate. The engaging projecting portions in the regions of the ends of the visor and the vicinities thereof, which are inserted into the visor attachment portions, are prevented by the click function of the engaging projecting portions and the visor attachment portions from being removed from the visor attachment portions.
In the visor attachment mechanism of the patent literature, the regions of the left and right ends of the visor and the vicinities thereof are prevented by the click function of the engaging projecting portions that jut out in the regions of the ends and the vicinities thereof and the pair of left and right visor attachment portions from being removed from the pair of left and right visor attachment portions. Hence, when the attachment mechanism of the engaging projecting portions to the visor attachment portions is designed to weaken the click function, the regions of the ends of the visor and the vicinities thereof can easily be attached to and detached from the visor attachment portions. In this case, however, the regions of the ends of the visor and the vicinities thereof are readily removed from the visor attachment portions accidentally. Conversely, when the attachment mechanism of the engaging projecting portions to the visor attachment portions is designed to enhance the click function, the regions of the ends of the visor and the vicinities thereof are hardly removed from the visor attachment portions accidentally. In this case, however, the regions of the ends of the visor and the vicinities thereof are hard to attach to and detach from the visor attachment portions.
On the other hand, when the attachment mechanism of the engaging projecting portions to the visor attachment portions is designed to obtain a click function with an appropriate strength, the regions of the ends of the visor and the vicinities thereof can relatively easily be attached to and detached from the visor attachment portions. Additionally, in this case, accidental removal of the regions of the ends of the visor and the vicinities thereof from the visor attachment portions is relatively rare. However, to adjust the click function to an appropriate strength, it is necessary to increase the accuracy of the manufacturing process of the regions of the ends of the visor and the vicinities thereof and the movable plate, and the size adjustment process of the regions of the ends of the visor and the vicinities thereof and the movable plate. In this case, it is therefore difficult to mass-produce the visor attachment mechanism.